1. Field of the Invention
The present application relates generally to electro-hydraulic servo loops, in particular, to the detection of faults and degradation in servo loops.
2. Description of Related Art
Servo-valves have been around for many years. Servo valves are used in many applications, such as the delivery of fuel to a helicopter engine. Servo valves are typically configured to move an actuator allowing fuel to be dispersed in an engine. Actuators in the servo valve can degrade over time and wear. At such times, the actuators typically fail to perform as required or expected.
Different methods have been utilized to measure when the hydraulic servo valve has degraded. A position sensor may be used to compare the actual measured position to the predicted position of the hydraulic servo valve based on a model of the closed loop dynamics. The disadvantage of this method is that significant degradations can sometimes result in only subtle differences in the position sensor value. Thus, detecting failures may often require major degradation.
Additionally, a persistence monitor may be used to detect degradation of fuel servo valves. A persistence monitor typically requires a failure to be true for a specified period of time. The disadvantage of this system is that it is often not robust enough to detect oscillatory failures where the monitor value will intermittently exceed the threshold.
Additional monitors and instruments may be added at intermediate stages of the hydraulic servo valve in an attempt to detect such failures, however, this method often requires additional wires/interface, resulting in a weight, space, and complexity increase. Even with the additional instrumentation, a method of detecting oscillatory failures still needs to be defined.
Although great strides have been made in detecting degradation of servo valves, considerable shortcomings remain.
While the system and method of the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the application to the particular embodiment disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the process of the present application as defined by the appended claims.